Method and structure for processing thin film PV cells with improved temperature uniformity

Abstract

An apparatus for reactive thermal treatment of thin film photovoltaic devices includes a furnace tube including an inner wall extended from a first end to a second end. The apparatus further includes a gas supply device coupled to the second end and configured to fill one or more working gases into the furnace tube. Additionally, the apparatus includes a cover configured to seal the furnace tube at the first end and serve as a heat sink for the one or more working gases. Furthermore, the apparatus includes a fixture mechanically attached to the cover. The fixture is configured to load an array of substrates into the furnace tube as the cover seals the furnace tube. Moreover, the apparatus includes a crescent shaped baffle member disposed seamlessly at a lower portion of the inner wall for blocking a convection current of the one or more working gases cooled by the cover.

1. An apparatus for reactive thermal treatment of thin film photovoltaic devices, the apparatus comprising:
 a furnace tube including an inner wall extended from a first end to a second end; 
 a gas supply device coupled to the second end and configured to fill one or more working gases into the furnace tube; 
 a cover configured to seal the furnace tube at the first end and serve as a heat sink for the one or more working gases; 
 a fixture mechanically attached to the cover, the fixture being configured to load an array of substrates into the furnace tube as the cover seals the furnace tube; and 
 a shaped baffle member disposed seamlessly at a lower portion of the inner wall for blocking a convection current of the one or more working gases cooled by the cover. 
 
     
     
       2. The apparatus of  claim 1  further comprising a heater disposed outside to heat the furnace tube using thermal radiation. 
     
     
       3. The apparatus of  claim 2  wherein the furnace tube comprises quartz material at least semitransparent to the thermal radiation. 
     
     
       4. The apparatus of  claim 2  wherein the thermal radiation can heat the array of substrates and the one or more working gases, resulting in a temperature profile associated with the array of substrates. 
     
     
       5. The apparatus of  claim 4  wherein the temperature profile does not vary more than 20° C. for the array of substrates each having a size of 20×20 cm. 
     
     
       6. The apparatus of  claim 4  wherein the shaped baffle is configured as a crescent shaped baffle member, the crescent shaped baffle member restricts a convection current of the one or more working gases being heated substantially within a spatial region between the crescent shaped baffle member and the second end. 
     
     
       7. The apparatus of  claim 6  wherein the cover comprises a surface capable of absorbing solid-phase residue particles mixed with the one or more working gases flowing above the crescent shaped baffle member from the spatial region. 
     
     
       8. An apparatus for uniform thermal treatment of thin film devices, the apparatus comprising:
 a furnace tube including a circular inner wall extended along an axial direction in horizontal direction from a first end region to a second end region; 
 a gas supply device coupled to the second end region for filling a work gas into the furnace tube; 
 a cover member configured to seal the furnace tube at the first end region; 
 a rack fixture mechanically attached to the cover member, the fixture being configured to load a plurality of substrates into the furnace tube as the cover member seals the furnace tube; 
 a heater surrounded the furnace tube to provide thermal radiation from outside to heat the work gas; and 
 a baffle member disposed at a lower portion of the circular inner wall. 
 
     
     
       9. The apparatus of  claim 8  wherein the furnace tube comprises a quartz material having a circular internal cross section and being at least semitransparent to the thermal radiation. 
     
     
       10. The apparatus of  claim 9  wherein the rack fixture comprises one or more disk members separating the cover member and the array of substrates, each disk member being configured to have a circular shape covering major portion of the internal cross section except a peripheral gap off the circular inner wall. 
     
     
       11. The apparatus of  claim 10  wherein the peripheral gap has a dimension smaller than 0.6 inches in radial direction. 
     
     
       12. The apparatus of  claim 10  wherein the baffle member comprises two or more segments end-to-end coupled together to form a crescent shaped assembly with a dimension in radial direction that is at least greater than the peripheral gap. 
     
     
       13. The apparatus of  claim 12  wherein each segment comprises a chord having a subtended angle to provide a total angle of 150 degrees or greater for the crescent shaped assembly. 
     
     
       14. The apparatus of  claim 13  wherein the baffle member is configured to be in contact with at least one of the one or more disk members to use the crescent shaped assembly for substantially blocking a 150-degree section of the peripheral gap off the lower portion of the circular inner wall. 
     
     
       15. The apparatus of  claim 13  wherein the cover member comprises an internal cooling structure configured to provide a cold surface capable of cooling a current of the work gas flowing from a 210-degree section of the peripheral gap of the upper portion of the circular inner wall to the first end region and absorbing residue particles in the work gas. 
     
     
       16. The apparatus of  claim 15  wherein the baffle member is configured substantially preventing the cooled current of the work gas to return from the first end region to the plurality of substrates for maintaining a temperature variation no more than 20° C. for each of the plurality of substrates across an area of 20×20 cm.